Btrfs: Properly handle overlapping extent in shrink_extent_tree

The patch fixes the overlapping extent issue in shrink_extent_tree.
It checks whether there is an overlapping extent by using
find_previous_extent. If there is an overlapping extent, it setups
key.objectid and cur_byte properly.

---

Signed-off-by: Chris Mason <chris.mason@oracle.com>

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index cc89df4493abf21445b4497a09ebc8638814c0d0..426a0222e12f7c4474d3aa0077af69b8808369a4 100644 (file)
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -2317,36 +2317,6 @@ out:
        return ret;
 }
 
-static int find_overlapping_extent(struct btrfs_root *root,
-                                  struct btrfs_path *path, u64 new_size)
-{
-       struct btrfs_key found_key;
-       struct extent_buffer *leaf;
-       int ret;
-
-       while(1) {
-               if (path->slots[0] == 0) {
-                       ret = btrfs_prev_leaf(root, path);
-                       if (ret == 1) {
-                               return 1;
-                       }
-                       if (ret < 0)
-                               return ret;
-               } else {
-                       path->slots[0]--;
-               }
-               leaf = path->nodes[0];
-               btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
-               if (found_key.type == BTRFS_EXTENT_ITEM_KEY) {
-                       if (found_key.objectid + found_key.offset > new_size)
-                               return 0;
-                       else
-                               return 1;
-               }
-       }
-       return 1;
-}
-
 int btrfs_shrink_extent_tree(struct btrfs_root *root, u64 new_size)
 {
        struct btrfs_trans_handle *trans;
@@ -2357,11 +2327,10 @@ int btrfs_shrink_extent_tree(struct btrfs_root *root, u64 new_size)
        struct btrfs_fs_info *info = root->fs_info;
        struct extent_map_tree *block_group_cache;
        struct btrfs_key key;
-       struct btrfs_key found_key = { 0, 0, 0 };
+       struct btrfs_key found_key;
        struct extent_buffer *leaf;
        u32 nritems;
        int ret;
-       int slot;
 
        btrfs_set_super_total_bytes(&info->super_copy, new_size);
        block_group_cache = &info->block_group_cache;
@@ -2372,48 +2341,54 @@ int btrfs_shrink_extent_tree(struct btrfs_root *root, u64 new_size)
 again:
        total_found = 0;
        key.objectid = new_size;
-       cur_byte = key.objectid;
        key.offset = 0;
        key.type = 0;
-       while(1) {
+       cur_byte = key.objectid;
 
+       ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
+       if (ret < 0)
+               goto out;
+
+       ret = find_previous_extent(root, path);
+       if (ret < 0)
+               goto out;
+       if (ret == 0) {
+               leaf = path->nodes[0];
+               btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
+               if (found_key.objectid + found_key.offset > new_size) {
+                       cur_byte = found_key.objectid;
+                       key.objectid = cur_byte;
+               }
+       }
+       btrfs_release_path(root, path);
+
+       while(1) {
                ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
                if (ret < 0)
                        goto out;
-next:
+
                leaf = path->nodes[0];
-               if (key.objectid == new_size - 1) {
-                       ret = find_overlapping_extent(root, path, new_size);
-                       if (ret != 0) {
-                               btrfs_release_path(root, path);
-                               ret = btrfs_search_slot(NULL, root, &key,
-                                                       path, 0, 0);
-                               if (ret < 0)
-                                       goto out;
+               nritems = btrfs_header_nritems(leaf);
+next:
+               if (path->slots[0] >= nritems) {
+                       ret = btrfs_next_leaf(root, path);
+                       if (ret < 0)
+                               goto out;
+                       if (ret == 1) {
+                               ret = 0;
+                               break;
                        }
+                       leaf = path->nodes[0];
+                       nritems = btrfs_header_nritems(leaf);
                }
-               nritems = btrfs_header_nritems(leaf);
-               ret = 0;
-               slot = path->slots[0];
-               if (slot < nritems)
-                       btrfs_item_key_to_cpu(leaf, &found_key, slot);
-               if (slot == nritems ||
-                   btrfs_key_type(&found_key) != BTRFS_EXTENT_ITEM_KEY) {
+
+               btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
+               if (btrfs_key_type(&found_key) != BTRFS_EXTENT_ITEM_KEY ||
+                   found_key.objectid + found_key.offset <= cur_byte) {
                        path->slots[0]++;
-                       if (path->slots[0] >= nritems) {
-                               ret = btrfs_next_leaf(root, path);
-                               if (ret < 0)
-                                       goto out;
-                               if (ret == 1) {
-                                       ret = 0;
-                                       break;
-                               }
-                       }
                        goto next;
                }
-               btrfs_item_key_to_cpu(leaf, &found_key, slot);
-               if (found_key.objectid + found_key.offset <= cur_byte)
-                       continue;
+
                total_found++;
                cur_byte = found_key.objectid + found_key.offset;
                key.objectid = cur_byte;
@@ -2446,33 +2421,30 @@ next:
                ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
                if (ret < 0)
                        goto out;
-bg_next:
+
                leaf = path->nodes[0];
                nritems = btrfs_header_nritems(leaf);
-               ret = 0;
-               slot = path->slots[0];
-               if (slot < nritems)
-                       btrfs_item_key_to_cpu(leaf, &found_key, slot);
-               if (slot == nritems ||
-                   btrfs_key_type(&found_key) != BTRFS_BLOCK_GROUP_ITEM_KEY) {
-                       if (slot < nritems) {
-                               printk("shrinker found key %Lu %u %Lu\n",
-                                      found_key.objectid, found_key.type,
-                                      found_key.offset);
-                               path->slots[0]++;
-                       }
-                       if (path->slots[0] >= nritems) {
-                               ret = btrfs_next_leaf(root, path);
-                               if (ret < 0)
-                                       break;
-                               if (ret == 1) {
-                                       ret = 0;
-                                       break;
-                               }
+bg_next:
+               if (path->slots[0] >= nritems) {
+                       ret = btrfs_next_leaf(root, path);
+                       if (ret < 0)
+                               break;
+                       if (ret == 1) {
+                               ret = 0;
+                               break;
                        }
+                       leaf = path->nodes[0];
+                       nritems = btrfs_header_nritems(leaf);
+               }
+
+               btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
+               if (btrfs_key_type(&found_key) != BTRFS_BLOCK_GROUP_ITEM_KEY) {
+                       printk("shrinker found key %Lu %u %Lu\n",
+                               found_key.objectid, found_key.type,
+                               found_key.offset);
+                       path->slots[0]++;
                        goto bg_next;
                }
-               btrfs_item_key_to_cpu(leaf, &found_key, slot);
                ret = get_state_private(&info->block_group_cache,
                                        found_key.objectid, &ptr);
                if (!ret)